Indexing mechanism



Nov. 7, 1950 c, s, BEDNASH ETAL 2,528,489

INDEXING MECHANISM Filed April 4, 1946 Patented Nov. 7, 1950 UNITED STATES PATENT OFFICE INDEXING MEoHANIsM Application April 4,1946, seria1No'.659,560

(Cl. 19a-F149) 8 Claims.

This invention relates to mechanism for effecting the stoppage of motor-driven devices and more particularly for effecting and maintaining the stoppage of such devices in a given rotary position by a reversal in rotation.

When attempting to effect a stoppage of a rotary apparatus in a given rotary position, mechanisms designed for this purpose, available heretofore, have been found inadequate due to the rotary inertia of the apparatus which caused it to override a given position at which it had been stopped, thereby also affecting the positiveness of the stoppage.

It is an object of the present invention to provide a means for stopping a rotatably driven apparatus in a given rotary position by -application thereto of a reverse rotation at the time of stoppage.

It is another object to provide a mechanism of the type referred to which will impart a reversed rotation to a rotating apparatus upon stoppage thereof to return it to a predetermined rotary position from which it had departed due to inertia.

Still another object is to provide springactuated rotation-reversing means to return the rotary apparatus to a given rotary position after stoppage has been effected.

In accordance with our'invention, we provide in combination with a motor-driven rotary apparatus, a stopping mechanism on the driving shaft, including a rotary detent element adapted to be engaged by a stopping element arranged for separate rotary motion with respect to the drive shaft. There is also provided on the shaft, rotation-braking and spring-motor means Afor effecting reverse rotation. The braking means comprises, according to one of the features, a clutch mechanism, one part of which is secured to the shaft, the other being freely movable thereon. The movable part of the-clutch includes the spring-motor which, when the power tothe motor has been removed and the freely movable spring-urged clutch portion has made contact with the clutch portion rotating with the shaft, causes, after the rotary inertia of the motor has wound it, to reverse the rotation of the shaft until the spring has substantially unwound. The reverse motion causes the detent and stopping means to firmly engage in agiven rotary position as determined by the position given to the detent prior to the removal of power to the motor. In accordance with another feature of the invention, the clutch is replaced by a brake drum combination which becomes effective as the mQtor switchis opened.

These 'and other features and objects of the invention will be best understood from the following description of an embodiment thereof, reference being had to the drawings, in which:

Fig. l is an illustration, partly in section, of a rotary stopping mechanism and of the rotationreversal means in accordance with the invention;

Fig. 2 is a view in elevation of a motor 'and prony-type brake therefor including a spring means for rotation reversal; and

Fig. 3 Sis a view Vin the direction of the arrows of aisection III-III taken inthe View of Fig. 2.

Referring to Fig. `1 of the attached drawings there is showna `portion'of a motor I for'drving an apparatus (which has Vnot been shown) and which for instance,l may'be the tuning condenser of a radio communication apparatus as used in a scanning receiver. The motor I is provided with a dri-veshaft 2 for driving the rotary apparatus as Well as an adjustable indexing or stopping mechanism 3. This stopping mechanism may be one of many convenient types, preferably such as the ione illustrated, Vwherein a cam 4, provided with :a detent or stopping face 5 is fiXedly connected to a gear-6 which may be rotated through a gear -1 nand an adjusting knob 8 to any selected rotary position. :Directly mounted on the shaft -2 is a'rotating arm `9 vhaving a lever I0 pivoted thereon and urged against the cam 4 by means of a spring 'I I. When the shaft 2 is 'rotated in the direction of the arrow I2 at a normal operating speed, a -weight I3 at the end of the lever IIJ exerts a centrifugal force resulting in a position of Athe lever I0 effective in holding the stopping portion or face I4 'out of 'engagement with the detent 5.

In-addition, there is mounted on the shaft 2, a clutch mechanism I5 Ycornprisedof one clutch face I6 Xedly secured to the shaft 2 by means of a Apin I1. Another clutch face 'I8 is mounted Vto rotate freely on a sleeve I9 on the Shaft forming part'of an armature 28 of an electromagnet 2.I fastened to-the motor `I lpreferably-by means such as threaded bolts 22-23. ordinarily urged-away from the electromagnet or coil 2| by'means of expansion springs 25s mounted on the bolts 23. It will be seen thatV during rotationl of the'motor, the armature `does not rotateV but remains stationary due to its connection` with the housing of the motor through the bolts 23. The freely rotatable clutch plate I 3 is flexibly connected to the non-rotary armature '1Z0 by means of ahelical type spring 25, one end of which is anchored'tothe armature 25, the otherv endthereof bein'g'secured to the clutch plate `I3` The armature 20 `is* The arrangement is such that when motor I is in operation, the coil 2l is energized to hold the armature 29 and therewith the clutch face I8 away from the rotating clutch I6 against the compression of the springs 24. When the power to the motor is removed, the electromagnet 2I becomes de-energized and the springs 24 force the armature 20 and with it the clutch plate I8 into engagement with the clutch plate I6. Due to rotary inertia, the rotation of the rotor of the motor I persists for a short period and causes the clutch plate I6 fixed to the shaft and the plate I8 to rotate and to wind the spring 25, As the shaft 2v finally comes to rest, the tension in the wound spring 25 reverses the rotation of the sh-aft 2 carrying the arm 9 and level III at a relatively low speed so that the stopping face or portion I4 of the stopping mechanism 3 tends to positively engage the detent on the cam 4. The spring 25 is preferably of sufficient length to provide for several revolutions of the shaft after the motor has been stopped so that a continuous and positive urge is effective on the lever I0 with respect to the detent 5 regardless of the adjustment of the cam 4. It is apparent that the helical spring 25 may be replaced by a coil spring, such as ordinarily used in watches.

In the other form of the invention, shown in Figs. 2 and 3, a motor 28, which is provided with a drive shaft 29 for rotating suitable rotary apparatus, as well as an indexing mechanism, as described in connection with Fig. 3, has been provided with a freely rotatable brake drum or disk 30 to which is Alixedly attached at 3| one 'end of a spiral or helical spring 32. The power supply circuit for the motor includes wire conductors 33 and a switch box 34, the switch of which is operated by a lever 35. Mounted on a shaft 36 provided for operating the switch 34 by means of the lever 30, is a brake shoe 31 for application to the brake drum 30.

Thus, when it is desired to stop the apparatus at a given selected position, the power supplied to the motor is interrupted by operation of the lever 35 opening the switch 34, simultaneously applying the brake shoe 31 to the drum 3 I, which tends to stop the rotation thereof. The inertia of the shaft 29 and of the motor rotor continues to rotate the shaft in the direction of the arrow 3B for a few revolutions to wind the spring 32 between the shaft 29 and the braked drum 30. After the rotation due to this inertia has stopped, the tension in the spring 32 will cause the shaft 29 slowly to reverse its rotation. This will effect a positive engagement of the detent and stopping portions of the indexing mechanism as described in connection with Fig. 1.

It will be apparent from the above description that the inherent advantage of this device .lies in the fact that it is unnecessary to reverse the power of the motor in order to obtain a reversal of the driving shaft for positively operating the indexing or stopping mechanism.

While we have described above the principles of our invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of our invention as set forth in the objects hereof.

We claim:

1. For use with a rotatable device which it is desired to stop in a given rotary position, a stopping system, comprising a shaft, power means :for driving said shaft; means for stopping said shaft arranged to become eifective upon the removal of power from said driving means including detent means and means for engaging said detent in a rotary sense opposite to the normal one for said shaft, said engaging means being arranged to be rotated by the shaft and said detent means being independently rotatable to selected rotary positions; means for braking the rotation of said shaft, and spring motor means arranged to be energized for reverse rotation of said shaft upon said braking means becoming effective, whereby a given period after said braking means has become effective said spring motor means causes said shaft to reverse its rotation to eifect a positive operation of said stopping means in a predetermined rotary position.

2. A system according to claim l, wherein said braking means comprises a clutch including means for maintaining it inoperative during operation of said shaft by said power means.

3. A system according to claim 1, wherein said braking means comprises a clutch including electromagnet means for maintaining it inoperative during operation of said shaft by said power means.

4. A system according to claim 1, wherein said braking means comprises a clutch having a portion rotating with said shaft and a` freely rotatable second portion, and said spring motor comprises a helical spring operatively connected to said second portion to be wound by the rotation thereof.

5. A system according to claim 1, wherein said braking meanscomprises a friction brake, and means for actuating said brake.

6. A system according to claim 1, wherein said braking means `comprises a friction brake including a freely rotatable brake drum and a brake shoe, and said spring motor means comprises a helical spring operatively connected between said` 7. For use with a rotatable device which it desired to stop in a given rotary position, a stopping system, comprising a shaft, power means for driving said shaft; means for stopping said shaft arranged to become effective upon the removal of power from said driving means including detent means and means for engaging said detent in a rotary sense opposite to the normal one for said shaft, said engaging means being arranged to be rotated by said shaft and said detent means being independently rotatabley to selected rotary positions; friction clutch means for braking reverse rotation of said shaft, an electromagnet formaintaining said clutch inoperative during shaft rotation by said power means, spring means normally urging said clutch into operative position, spring motor means operatively connected between a xed portion of said system and said clutch to be energized by said clutch for reverse rotation of said shaft upon the said clutch becoming effective, and means to render said rclutch effective upon de-energizationof said power means; whereby a given period after said clutch has become eifective said spring motor means causes said shaft to reverse its rotation to eiTect a positive operation of said stopping means in a predetermined rotary position.

8. For use with a rotatable device which it isY desired to stop in a given rotary position, a stopping system, comprising a shaft, an electric motor4 including power control means for rotating said shaft, means for stopping said shaft arranged to become eifective upon the removal of power from,A

said motor including detent means and means for engaging said detent in a rotary sense opposite to the normal one for said shaft, said engaging means being arranged to be rotated by said shaft and said detent means being independently r0- tatable to selected rotary positions; friction brake means including a brake drum and a brake shoe for braking the rotation of said shaft, means for simultaneously operating said power control and said brake shoe, and spring motor means operatively .connected between said drum and said shaft to be energized by said shaft for reverse rotation of the shaft upon said braking means becoming effective, whereby a given period after said REFERENCES CITED The following references are of record in the l0 file of this patent:

FOREIGN PATENTS Country Date France J an. 8, 1925 Number 

